Foreign hackers have attacked an estimated 1,500 Vietnamese websites, including the online forum for white-hat hackers, since early this month.
The list of hacked websites ranges from government sites to sites dealing with real estate and electronics.
In the latest case, Kon Tum Province's Department of Education and Training's website was disrupted on Wednesday.
On June 5, www.hvaonline.net, a popular forum for legitimate web security technicians (aka white-hat hackers) fell prey to a staunch attack.
The hackers allegedly deployed a Distributed Denial-of-Service attack (DDoS attack).
The website's service provider announced that most of the hackers had Chinese IP addresses.
Shortly after the website was restored, on June 12, it was hit by another DoS attack.
The Vietnam National Oil and Gas Group (PetroVietnam)'s site, petrotimes.vn, and a website used by the Vietnamese Ministry of Foreign Affairs were also hacked.
IT experts said the DDoS attacks did not cause huge losses to Vietnamese websites because they could not change the content of the websites.
The hackers used the attacks just to show what they are capable of, they said.
According to commenters in a number of popular IT forums, a number of Vietnamese companies and agencies were poorly equipped to deal with the online assault.
"Foreign hackers are launching organized and deliberate attacks on Vietnamese websites," said Vo Do Thang, director of Athena Network Security Center in Ho Chi Minh City.